Objective: To study the compliance and changes in plasma lipids, plant sterols, fat-soluble vitamins and carotenoids in children and parents with familial hypercholesterolemia (FH) consuming a plant sterol ester-enriched (PSE) spread. Design: A 26-week open-label follow-up of children who had previously been studied in a controlled cross-over design. The parents were also included in the open-label arm of the study. Setting: Outpatient clinic for treatment of hyperlipidemia. Subjects: A total of 37 children (7 - 13 y) and 20 parents (32 - 51 y) diagnosed with 'definite' or 'possible' heterozygous FH. In all, 19 of the parents, but no children, used statins. All were patients at the Lipid Clinic, National Hospital in Oslo. Interventions: Subjects were recommended to eat 20 g/day of PSE spread as part of their lipid-lowering diet. Results: The mean intake of PSE spread was 13.7 and 16.5 g/days in the children and parents, respectively, corresponding to 1.2 and 1.5 g of plant sterols. Plasma total cholesterol decreased by 9.1% in both children (P<0.001) and parents (P = 0.002). The corresponding decreases in LDL cholesterol were 11.4% (P<0.001) and 11.0% ( P = 0.012). Increases in serum lathosterol, campesterol and sitosterol, adjusted for total cholesterol, were observed in the children (31, 96, 48%, respectively, P<0.001) at the end of the controlled cross-over period. In the parents, serum campesterol and sitosterol, adjusted for total cholesterol, increased by 92 and 39%, respectively (P<0.001). Lipid-adjusted serum alpha- and beta-carotene decreased by 17.4% (P = 0.008) and 10.9% ( P = 0.018), respectively, in the children at the end of the controlled PSE period, but increased again during the follow-up. In the parents, serum alpha- and beta-carotene concentrations were unchanged, while serum lutein and lycopene decreased by 7.3% (P = 0.037) and 14.6% (P = 0.044), respectively. Conclusions: Sustained efficacy of cholesterol reduction and long-term compliance of PSE intake were demonstrated in this study. Sponsorship: Unilever Research and Development, Vlaardingen, The Netherlands.